1. Field of the Invention
This invention relates to a wear sensor disposed to closely face the inner space of, for example, the cylinder incorporating a piston, and used for sensing wear of the inner wall or the like of the cylinder directly or indirectly.
2. Description of the Prior Art
The inner wall of a cylinder wears with reciprocal movement of a piston and conventional practice to find wear or the degree of wear has depended on visual observation after disassembling the cylinder when vibration arising from wear is sensorially recognized with the sense of hearing.
In short, when wear develops in an internal part of a unit, for example, the cyinder as described above, troublesome work is required for disassembling and thereafter, reassembling the unit. With respect to those units that are impossible to disassemble because of the use or the mechanism thereof, vibration caused by wear is observed by means of vibrograph, by which wear is indirectly observed. However, vibration is caused not only by wear but also by other factors. On the contrary, no vibration is caused sometimes even if wear develops. Therefore, such a method as indirect observation cannot reliable.